Calculating maximum and minimum values in an array

Question

I have an array of integers and need to find the position in the array of the maximum number along with the minimum. I have it working but it doesn't seem to be a very good way to do it. Can anyone suggest a better way to achieve what I have?

Here's my code:

int[] usageHours = { 3, 3, 5, 4, 0, 0, 2, 2, 4, 25, 158, 320, 212, 356, 401, 460, 480, 403, 298, 213, 102, 87, 34, 45 };
double myAverage = usageHours.Average();
int runningTotal = 0;
int runningMaxPosition = 0;

for (int i = 0; i < usageHours.Length; i++)
{
    if (usageHours[i] > runningTotal)
    {
        runningMaxPosition = i;
        runningTotal = usageHours[i];
    }
}

txtmax.Text = Convert.ToString(runningMaxPosition)+" With: "+Convert.ToString(runningTotal)+" Users";
txtAv.Text = Convert.ToString(myAverage);

Answer 1

That code is mostly fine. I'd suggest changing the variable names a bit, but that's all. You can work out the minimum in the same loop. I've changed the "if" conditions very slightly to guarantee that they always pick out at least one element (even if all the values are, say, int.MinValue). There are other ways of approaching this, but this is one example. If you have an empty array, you'll end up with max=min=0, and both indexes=-1.

int currentMax = 0;
int currentMaxIndex = -1;
int currentMin = 0;
int currentMinIndex = -1;

for (int i = 0; i < usageHours.Length; i++)
{
    if (currentMaxIndex == -1 || usageHours[i] > currentMax)
    {
        currentMaxIndex = i;
        currentMax = usageHours[i];
    }
    if (currentMinIndex == -1 || usageHours[i] < currentMin)
    {
        currentMinIndex = i;
        currentMin = usageHours[i];
    }
}

Here's an alternative using nullable value types to represent "there were no values" answers:

int currentMax? = null;
int currentMaxIndex? = null;
int currentMin? = null;
int currentMinIndex? = null;

for (int i = 0; i < usageHours.Length; i++)
{
    if (currentMax == null || usageHours[i] > currentMax.Value)
    {
        currentMax = i;
        currentMax = usageHours[i];
    }
    if (currentMin == null || usageHours[i] < currentMin.Value)
    {
        currentMinIndex = i;
        currentMin = usageHours[i];
    }
}

Don't worry if you haven't come across nullable value types yet though...

Answer 2

The code looks OK for finding the max value. If you are using C# 3 or later you could use the LINQ extension methods (there are Min, Max and Average methods, and on List there is also a FindIndex method, amongst others), but I get the impression that you are learning programming, and then it is sometimes a good idea to implement stuff that may be built into the framework, just for the learning value.